1. Field of the Invention
The present invention relates to a multi-layer coating composition in a container for promoting rapid clotting of a blood sample, methods for applying the multi-layer coating composition in a container such as a blood collection device and a barrier package for the blood collection device.
2. Description of Related Art
Blood samples are routinely taken in evacuated collection tubes. One end of a double-ended needle is inserted into a patient""s vein. The other end of the needle then punctures a septum covering the open end of the tube so that the vacuum in the tube draws the blood sample through the needle into the tube. Using this technique, a plurality of samples can be taken using a single needle puncture of the skin.
Blood collected in evacuated tubes often must be clotted prior to clinical examination. It is desirable to form a dense clot as rapidly and completely as possible to facilitate clean separation of the clot from the serum layer by centrifugation. To achieve this, collection tubes frequently employ a clot activator. Typical activators are diatomaceous earth and particles of inorganic silicates, or biochemicals such as ellagic acid, thrombin and thromboplastin.
Two types of activators, classified in the art according to the portion of the blood coagulation cascade stimulated, are conventionally employed. Particulate activators share a common biochemical mechanism of clot activation known as contact activation of the intrinsic pathway. Whole blood contains all of the necessary factors to cause clotting by the intrinsic pathway. Clot activation by the intrinsic pathway is surface area dependent, i.e., the time required to form a complete blood clot is dependent on the total number of activating surface sites per unit area on the activator surface relative to the volume of blood. Greater surface area, provided by finely divided particulate activators, leads to shorter clot times. Particulate activators are used in practically all commercial blood collection tubes and lead to dense, crosslinked clots that cleanly separate from the serum in a centrifuge. Clot formation, however, is relatively slow, and about 30-60 minutes are required prior to centrifugation. Typical particulate activators used commercially are silica impregnated in fabric silica particles in small plastic cups or silicate particles applied to the tube wall in polyvinylpyrrolidone (PVP).
The second type of clot activators induces clotting through a different part of the coagulation cascade known in the art as the extrinsic pathway. The extrinsic system relies on the presence of a substance not normally present in whole blood. Activation is biochemical in nature and is concentration dependent. Clot activation rates lead to clot formation in 10-20 minutes, but clots resulting from the extrinsic pathway are gelatinous in nature and do not cleanly separate from serum.
There is a need for a blood collection tube with means for promoting clot acceleration of a blood sample which provides an enhanced rate of blood coagulation but which does not remain in the serum layer but becomes part of the clot upon centrifugation, thus avoiding potential interference with clinical tests.
The present invention is a container with means for promoting clot acceleration of a blood sample. Desirably, the container comprises a coating of an intrinsic coagulation activator and an extrinsic coagulation activator.
Preferably, the intrinsic coagulation activator is diatomaceous earth or ground silica. Most preferably, the intrinsic coagulation activator is ground silica. Desirably, the intrinsic activator, for example ground silica, is applied with polyvinylpyrrolidone.
Desirably, the extrinsic coagulation activator is ellagic acid or a protein. Preferably, the extrinsic coagulation activator is thrombin, heparinase or fibrinogen. Most preferably, the extrinsic coagulation activator is thrombin.
The intrinsic coagulation activator and the extrinsic coagulation activator are applied to interior surfaces of a container, such as a blood collection tube, in the form of mixtures or solutions. The mixtures or solutions are dried to form layers of the activators. Additionally, other layers of additional materials may suitably be applied. Alternatively, different activators and materials may be mixed to form combined solutions which may be applied and dried to form a layer or layers having the combined attributes of the solution constituents.
In one aspect of the present invention, the means for promoting clot acceleration is applied as a dual-layered coating to the inside of a container as follows:
(a) mixing polyvinylpyrrolidone (PVP) and an intrinsic coagulation activator in water to form a first mixture;
(b) spraying the first mixture onto the inner surface of the container;
(c) drying the first mixture to form a first coating layer;
(d) mixing an extrinsic coagulation activator with water to form a second mixture;
(e) spraying the second mixture onto the first coating layer; and
(f) drying the second mixture to form a second coating layer.
Preferably, the means for promoting clot acceleration is applied as a dual-layered coating to the inside of a container as follows:
(a) mixing polyvinylpyrrolidone (PVP), an intrinsic coagulation activator and a water soluble surfactant in water to form a first mixture;
(b) spraying the first mixture onto the inner surface of the container;
(c) drying the first mixture to form a first coating layer;
(d) mixing an extrinsic coagulation activator with water to form a second mixture;
(e) spraying the second mixture onto the first coating layer; and
(f) drying the second mixture to form a second coating layer.
More preferably, the means for promoting clot acceleration is applied as a dual-layered coating to the inside of a container as follows:
(a) mixing polyvinylpyrrolidone (PVP), ground silica and a water soluble silicone surfactant in water to form a first mixture;
(b) spraying the first mixture onto the inner surface of the container;
(c) drying the first mixture to form a first coating layer;
(d) mixing thrombin with water to form a second mixture;
(e) spraying the second mixture onto the first coating layer; and
(f) drying the second mixture to form a second coating layer.
In another aspect of the present invention, the means for promoting clot acceleration is applied as a three-layered coating to the inside of a container as follows:
(a) mixing a water soluble surfactant with water to form a first mixture;
(b) spraying the first mixture onto the inner surface of the container;
(c) drying the first mixture to form a first coating layer;
(d) mixing polyvinylpyrrolidone (PVP) and an intrinsic coagulation activator in water to form a second mixture;
(e) spraying the second mixture onto the first coating layer;
(f) drying the second mixture to form a second coating layer;
(g) mixing an extrinsic coagulation activator with water to form a third mixture;
(h) spraying the third mixture onto the second mixture; and
(i) drying the third mixture to form a third coating layer.
Desirably, the means for promoting clot acceleration is applied as a three-layered coating to the inside of a container as follows:
(a) mixing a water soluble silicone surfactant with water to form a first mixture;
(b) spraying the first mixture onto the inner surface of the container;
(c) drying the first mixture to form a first coating layer;
(d) mixing polyvinylpyrrolidone (PVP) and ground silica in water to form a second mixture;
(e) spraying the second mixture onto the first mixture;
(f) drying the second mixture to form a second coating layer;
(g) mixing thrombin with water to form a third mixture;
(h) spraying the third mixture onto the second mixture; and
(i) drying the third mixture to form a third coating layer.
In addition, the container with the intrinsic and extrinsic coagulation activators is provided in a moisture impermeable receptacle with a moisture absorbing material. The moisture impermeable receptacle with a moisture absorbing material maintains the integrity of the thrombin in the container. Since thrombin may degrade when exposed to high external humidity, the integrity for promoting clot acceleration of a blood sample with thrombin is found to be maintained in a moisture impermeable receptacle.
Most notably, the present invention provides the means for promoting clot acceleration of a blood sample at a faster rate than when only silica is used.
In addition, the present invention provides the means for promoting clot acceleration of a blood sample even when exposed to high humidity.